Telephone system



,C. C. BRADBURY.

TELEPHONE SYSTEM.

APPLICATION men MAY16|1910,-

Patented May 10,1921.

3 SHEETS-SHEET1.

' InvE'nTm" VVI'InE 5 5 E 5 Patented May 10,1921.

3 SHEETSSHEET 2.

C. C. BRADBURY.

TELEPHONE SYSTEM,

APPLICATION FILED MAYIG, 910.

InvenIur NR N an Wifn E 5 5 E 5 %5 C. C. BRADBURY.

TELEPHONE SYSTEM.

APPLICATION FILED MAY16,1910.

1 77,555. Patented May 10, 1921.

3 SHEETS-SHEET'6.

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E Y H a a E; N m J I F WIIHESEEE' lnvenfnr UNITED STATES P TENT,fort es. I

CLIFFORD c; BEAJJB RYQQE 'RocHEsTEn' NEw Yonmnssieivon, izY iviEsNE ASSIGN- MENTS, To WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

To all whom it may concern/f.

Be it known that I, CLI E RD C. .BRAD- BURY, a citizen of the United States, residing in Rochester, county of Monroe, and

State of New York, have invented a certain new andusefulImprovement 1n Telephone Systems, of whichthe following is a specificationf 7' My invention relatesto telephone systems and particularly to that type of system:

using automatic or mechanical means at the central ofiice as an aid in establishing the connection tions. I

An object of the present invention is to provide a system which is readily convertible from the so-called call-distributing to full automaticsystem and also asystemfin which the apparatus individual to the line may be used in an exchange provided par'-' tially with full automatic equipmentv and partially with call-distributing equipment.

This feature of the invention becomes particularly desirable when an exchange, equipped for call-distributing, is changed over to an exchange of the full automatic type, since it is desirable to maintain serve iceon all of the lines during the change.

Myinvention also provides means where by subscribers who are willing to operate theirdials to make full automatic calls may obtain their connection through full automatic means at the central oflice'whereas those SubscribersQbJectmg to the use of the impulse sending device at the subscribers station may obtain theirconnection through the automatic call-distributing apparatus 5;

and a central oifice operator.

It is customary in manual'telephone systems to connect the sleeveor test contacts or the multiple jacks through the coil of automatic telephone systems to. connect the private or test contact of the connector:

switch multiple through the coil of a cutoff relay with the live or ungroundedpole of poleor" the central battery upon the sleeve of the multiple jackwill actuate thecut-ofl' relay and will connect the ground pole of f the central battery with the private contact calls. 1 between two SLlbSOITlbBIS ta-- TELEPHOEE SYSTEM. 5

V Specification of Letters Patent. Patented luay 1( 1921; Application filed May is, 19 0. Serial 'No. 561,766. i

of the connector I switch multiple of the same line, to establish the busy condition y for automatic subscribers, and whereby the connection of the ground pole of the central battery upon the private [contact of the" pole of the central battery to the sleeve contacts ofjthe multiple jacks of this same line to indicate the busy condition of the line to,

the operators who establish the manual A further object of invention is to so I organize my line circuit and apparatus as p to place the busy conditions before mentioned on both the sleeve contacts or the multiple' acks and the private contacts of the connector multiple when the line apparatus is-actuated-in initiating a call.

invention is illustrated in the accompanying drawing, in which all apparatusis Shown in its normal orunactuated condition.

Figure 1 represents a manual and an auto- 'matic subscribers station, each connected through SlIIlllaI llIle circuits and connector switches with the proper apparatus at the central oifice to complete. either the manual or the automatic. call asthecas'e may be.

Fig. 2 represents a connector circuitadapted to operatewith the lower of the subscribers" stations of Fig. 1, to establish an automatic connection either with the other subscribers line of F 1g. 1 or Wlth;

another automatic subscriben'and f Fig. 3. represents a cord or manual connecting circuit adapted to operate with the upper subscribers station and apparatus 01":

Fig. 1 to establish a manual connection between thatsubscriber and an automatic sul I scriber, such as the lower of Fig. 1 or any lOther manual subscribers line. a outwit relay to the ground pole of the central battery and it is-also customary in 7 It is to be understood that forlarge ex changes intermediate selector. switches may be. used between the line switches and the cord and connector circuits here illustrated, suitable switches and circuits for this purpose being illustrated in the coendin application ofCharles.-E.Hague, erial umber-556,924 filed April 22, 1910, now Patent v manently connected in a bridge between the and with the transmitter 9 and receiver 10 in a bridge maintained normally open by the contacts of the switch hook 11.

The impulse mechanism 8 comprises a dlal 12 having numerals thereon and having finger holds corresponding to the different numerals, by means of which the dial may be rotated in a clockwise direction until the finger strikes the stop 13. During the rota tion in this direction the roller 14 is moved about its pivot 15 such'that the contact spring 6 is not raised from its point 7, but upon the release of the dial 12 the mechanism is returned to its normal position by means of a spring, not shown in the drawing, and the roller 14 is caused to step over the dial of the star wheel 16, raising the spring 6 and interrupting the circuit between contacts 6 and 7 once for each tooth of the star wheel which passes under the roller.

At the central office line conductor 4 is mally open contacts 30 and 31 adapted,-

when the relay is actuated, to extend the limbs 4 and 5 of the telephone line through conductors '32 and 33 to the lever contacts 34 and 2350f relay 24, the lever 35 of this relay being normally connected through contact 36, conductor 37 and the coil 38 of cutoff relay 22 to earth. Conductor 3'? is also connected through conductor 40 and the coil 41 of line relay 28 with the normally open contact 42 of that relay. The other contact 4-3 of relay 28 is connected through conductor 44 with the private wire 45 and with the contact 46 of relay 24 and the contact 48 of relay 22. Contact 46 of relay 24 is'adapted to be connected through contact 49 of at relay with the private wire 50 extending to the private segment 51 of line switch 52. The normally closed contact 53 of relay 24 is connected with the lever contact 54 of relay 28 and thence throu h contact 55, conductor 56 and the coil 57 or relay 22 and conductor 29 to the live pole of battery A. Conductor 56 also connects through the coil 58 of relay 24 and conductor 59 with the contact lever 60 of relay 22, this lever being adapted to connect with contact48 of that relay before contact 48 breaks from its normal contact 01, this contact 61 being connected through the normally open contacts 62' and 63 relay 28 and the coil of motor magnet 64 and interrupter 65 with the live to connect with theileverrcontact 54 when the relay is actuated. Conductors, 32 and 33 are permanently connectcdthrough conductors 69'a'nd 70 with the multiple contacts 71 and 72 of the connector switch shown on Sheet 2 and with the tip and sleeve contacts 73 and 74 of the multiple jacks shown on Sheet 3. Relay 24 also has the normally open contacts 7 5 and '76 adapted to extend the line conductors 4 and 5 to the talking circuit segments 7'? and 78 of the line switch 52.

The line switch 52 which as here conventionally shown comprises a central shaft 80 upon which are mounted the ratchet wheel 81 and the insulated contact wipers 82, 83 and 84, these wipers being adapted to be rotated in a clockwise direction by means of the ratchet pawl 85 and the motor-magnet 64. ribout'the periphery of the line switch a plurality of contacts are held in insulated relation to one another, these contacts being connected with the various trunk circuits accessible to this particular line switch. It will be noted that between the talking circuit segments 77 and 'Z 8 there are two blank contacts 87 and 88 and that between segments T7 and 51 there is a single contact and between segments 78 and 51 there is a single contact. It will also be noted that the end contacts '89 and 90 opposite segment 51 are grounded. This arrangement permits the wipers 82 and 83 to pass oil of and onto the talking segments 77 and 78 without connecting these segments with earth.

Three of the contacts, 91, 92 and 93 of this line switch, are connected through conduc tors 94, 95 and 96 to the automatic connector circuit shown on Sheet 2, it being understood that the other contacts of the line switch are connected with other connector circuits similar to that on Sheet 2 and that contacts of a large number of line switches, preferably one hundred, are connected in multiple.

The manual telephone subscribers station 1 w and the apparatus individual thereto shown at the top of Sheet 1 is equipped with apparatus si; ,ilar to that formerly described with the exception of the automatic sending device at the substation, this latter being omitted from the equipment at substation 1, the corresponding apparatus of this line being designated by like figures with the suflix Referring now to Fig. 2 it will be seen that the top talking conductor 94 extends to the condenser 100 through conductor 101, normally open contacts 102 and 103 of relay 104, contacts 105 and 106 of ringing relay 107 and conductor 108 to the wiper 109, and that the lower talking conductor 95 extends through condenser 110, conductor 111, normally open contacts'112and 113 of relay 104, contacts 114 and 1150f ringing relay 107 and conductor 116 to the wiper 117.

The impulse relay 120 has its coil 121 connected between the talking conductor 94 and the ground pole oi the battery A and its coil 122 connected: between'the talking conductor 95 and the live pole of battery A; This relay controls normally open contacts 123 a and 124, contact 123 being connected to' ground and the contact 124 being connected to the private conductor 96 and also to the lever contact 125 of the slow acting relay 126. Lever contact 123 normally connects through contact 127 with the open contact 182 of relay 126.-w Relay 120 also has the lever contact 128 normally connecting with contact 129 and adapted upon the actuation ofthe relay to' connect 'with contact 130. The latter contact is connected through eon ductor 131 and the coil of relay 126 with the grounded contact normally connecting with the lever 142. a a l The lever contact128 of relay 120 connectedthrough conductor 148 and the .nor:

mal contacts 149'and 150 of relay 104 to earth,- conductor 148 being also connected. through the coil 151 of relay 104 toearth. The normally closed conta'ct129 of relay 120 is connected with the normally open contact 152 of relay 126, the lever contactl153fofthis relay being connected through conductor 154 andnormal contacts 155 and ofre-i lay 141 and, conductor 161 through thecoil of the vertical motor-magnet162' and con ductor 163 to the live pole-of battery IA. The. normally open contact 164 of relay 141 is connected through conductor165': and the I coil of the rotary motor-magnet- 1 66- and conductor 163 with the live pole ofbattery A;- The contact 153 of relay 126 is'alsoconnected through conductor 154 and conductor a 168 through the coil of, relay 138tothelive pole of battery A. I u r The coil of releasemagnet one ter;

minal connected through conductor 171 to the brush 17 2 ct interrupter'173 and has its other terminal connected through, comma tor 174 through normal contacts 175 and 176 V otrelay 177 andcontacts 181 and 1 80 of relay 126 through conductor 186 to, the nor,-

' mally open contact 183 of the vertical ofi' Contact 176' of normal bunch of springs. relay 177 is also connected to the normally open contact 184 of relay 133,' tl 1e lever con tact 185 'of thatrelay "being connected through conductor 186'to the samejcontact r 183 of the verticalofi-normal fbunch'of earth and the lower spring 189" is connected through. conductor 1'90 and the normal contacts1191 and-192, conductor. 193, normal springs. Themiddle spring188 of the vertical off-normal contacts is connected to contacts 194 and 195 of relay 138, conductor 196 andthe coil of relay 141 to the live pole of battery through conductor 197. The normally open contact 199,01 the rotary ofiy-nor- 3 mal-set of springs isconnected through conr i I ductor 200 with the open contact 201 of relay 138 and through contacts 202 and 203 of relay 141 and the coil'204of relay 104 to the live pole of battery A.

Therelay 177 has its coils 206 and ,207 I connected between talking conductors "101 and 111 and the opposite poles of the main batterylA. The normallylo'pen contact 208 of this relay isconnected with the normally closed contact209 of relay: 126. Relay 177 also has thefspring contact 210 connected with the normally open contact 211 of relay 104 and connecting through-the outside 'contact 212 and conductorj213 and the coil of ringing relay 107 to-the brush 2140f the ringing interrupter 173., The normally open contact 216 of relay 177 is connected throughthecoil 217 of relay 133 withithe live pole ofbatteryA. l-

The, normally closed outside contact 217 r of relay 104 is connected through conductor 218 with theinside contact 219 of relay 133, the lever contact 220 of this relay being connected through the secondary winding 221 0 1 the busy buzz induction coil 222 to earth,

The primary winding of thisinduction' coil is connected in series with the ra idinterrupter 223 and the main battery The relay107 hasthe normallyop'en contracts-225 and 226 adapted when the relay is actuatedto connect the brushes 227 and 228 ofringing generator 229 with the wipers 109 and 117, the'brush 228 being connected with the live pole'of battery A. I

a. With respect to the mech 'nisrn of the connecto'r switch shown upon Sheet 2 it is to'be ventionally illustrate an operative device. this illustration the niainsliaft 235 can the ratchet cylinder236 and the wipers 144, 109 and117andhas slidably secured to its upper end the rotary ratchet 237, this latterratchct being keyedto the shaft so tl'iat the shaft may be moved longitudinally through the, opening the, ratchet wheel but thatjthe rotary movement of the a ratchet andth'e shaft will'be as a'unit; Thestep by step vertical motion the shaft is accomplished. by .rneanslof the pawl 238 and the step by ste jrotary m fiement accomplished by the action of thepawl 239,

thefshaft being held in itsvarious positions 1 'cn'nderstood that the illustrationis intended (mly' toqshow snfilcientqmechanismto con- 115 'cord circuit shown on Sheet 3. strand 94 extends through the condenser of vertical and rotary movement by the double release dog 240. i

245, conductor 246, normal contacts 247 and 2480f the operators listening key 249, normal contacts 250 and 251 of the operators ringing key to the tip contact 252 of the calling plug and talking conductor 95 extends through condenser 254, conductor 255 and normal contacts 256 and 257 of the operators ringing key to the sleeve contact 258 of the calling plug. The calling plug also has a grounded ring contact 259.

The control relays 260 and 261 are connected in a bridge between talking conduc tors 94 and 95, this bridge containing the main battery A, while the control relays 262 and 263 are connected in a similar bridge between the talking conductors246 and 255. Relay 260 has the normally open contacts 272 and 273. contact 272 beingconnected with earth and contact 273 being connected through conductor 267 and the normal contacts 268 and 269 of relay 263 to the common wire 270, which is likewise connected to the similar contacts 269 of one half of the cord circuits appearing at'this particular operators position. Contact 272 of relay 260 also connects through the contacts 274 of key 275 to the private conductor 96, the actuation of key 275 being adapted tointerrupt the normal cont-acts and connect the conductor 96 to earth through contact 276. The control relay 261 has the normally open contacts 280 and 281, the lever 280 being connected through the call signal 282 with the live pole or battery A and the contact. 281 being connected through normal contacts283 and 284 of relay 263 to earth. The normally closed contact 285 of relay 261 is connected with the normally closed contacts 287 and 288 of relay 262 and the calling supervisory lamp 289 with the live pole of battery A. .Relay 263 also has the normally open contact 290 which is connected with earth and has the normally open contacts 291 and 292 adapted when closed to complete a shunt about the contacts 247 and 248 of the operators listening key 249. f

The operators communication set comprises thereceiver 294 and condenser 295, maintained in a normally open bridge by contacts 296 and 297 of the operators listening key, this bridge also containing the sec- 7 tion 1 to subscribers station 1.

ondary winding of the operators induction coil 298. The operators listening key also has a pair of auxiliary contacts 299 and 300 adapted upon the actuation of the listening key to complete a circuit through the tertiary winding of the operators induction coil 298. i

The operators ringing key has the normally open contacts 301 and 302, contact 301 being connected through the alternating current generator 305 to earth, and contact 302 being connected through the non-inductive resistance 304 to the live pole of battery A. I

The operation of my system will now be traced as it would occur: first, when a connection is completed from subscribers sta- In this instance subscriber in charge of substation 1 removes his receiver 10 from switchhook 11 and thereby completes a circuit from the live pole of battery A through conductor 29, coil 27 of relay 28, contacts 26 and 25 of relay 22, line conductor 5, con tacts 6 and 7 of the calling-mechanism 8,

transmitter 9, receiver 10, switch-hook 11, 7

line conductor 4, contacts 20 and 21 of relay'22 and coil 23 of relay 24 to ground. The current in'this path actuates relays 28 and 24 and thus completes a path for current from battery A through the interrupter 65. motor magnet 64, contacts 63 and 62 of relay 28, contacts 61 and 48 of relay22, contacts 46 and 49 of relay 24. conductor 50. segment 51, private brush 83 and the various' grounded contacts of busy trunk lines over which the brush 83 passes until arriving upon contact 93 whichis idle and is therefore not grounded.

Upon the private wiper passing onto a non-grounded contact, or if it were normally standing so, a surge of current will flow through conductor 44, contacts 43- and 42 and coil 41 of relay 28, conductor 40 and the coil 38 of relay 22 to ground. The impulse of current through the latter path is not suiiicienteto actuate the motor magnet 64, but. is sufficient lto actuate relay 22, changing its contacts to their abnormal condition and at the same time closing a looking circuit for relays 22, 24 and 28, which circuit may be traced from battery 29 through the coil 57 of relay 22, the coil 58 of relay 24, conductor 59, contacts 60 and 48 of relay 22, conductor 44, contacts 43 and 42 and coil 41 of relay 28, conductor 40 and the coil 38 of relay 22 to ground.

The actuation of relay 22 extends the limb 4 of the telephone line through contacts 20 and 30 of relay 22. contacts 34 and 75 of relay 24, segment 77, brush 82, and contact 91 of the line switch toconductor 94, and extends line conductor 5 through contacts 25 and 31 Of-relay 22, conductor 33, contacts 35 and 76 of relay 24, segment 78,

battery conductor 29, Sheet 2, through the 1 coil 122 ofrelay 120, conductor 95, contact 92, brush 84, segment 78, contacts 7 6 and-35 of relay 24, conductor33, contacts 31 and 25 of relay 22, lin'econductor 5, contacts 6.

and 7 of thesubscribers interrupter, transmitter 9, receiver 10, switch-hook 11,1ine

conductor 4, contacts20 and'30 of relay-22,

conductor 32, contacts 34 and of'relay 24, segment 77, brush 82, contact 91, conductor 94 and coil 121 of relay 120 to ground. :The'

current in this path actuates relay 120 which connects the private conductor 96 through contacts 124 and 123 of relay 120 to earth.

Thereupon a new circuit is completed from 1 the battery conductor 29, Sheet 1, through thecoil 57 of relay 22, coil 580i relay 24,

conductor 59, contacts 60 and 48 of relay 22',

contacts 46 and 49 of relay 24, conductor 50,

segment 51, brush-83, contact 93, conductor 96, and contacts 124 and 123 to; ground. The current in thispath maintains the actuation of relays 22 and 24 and the' ground upon conductor 50 shunts the coil-41 of line relay 28 so that that relaynow returns to its normal condition. This portionof the operation has occurred almost instantly and before the subscriber has had an opportunity to move his dial 12to call the'desired subscriber. I p p I The system here shown is illustrated without an intermediate or selector switch,-but it is to be understood that myinvention is 'ap-, plicable to systems of any size no matter what number of selector switches are applied. calling subscriber would operatehisdial but twice to receive the desired connection. The subscriber therefore places his finger in the finger hold'opposite the first figure in the number of the desired'subscriber androtates the dial 12.until the movement is interrupted by contact bet'Ween-theiinger and the*stop fore interrupts the circuit between contacts 13. During this rotation," the roller 14' swings to the right about its pivot15 and therefore does not raise the spring 6 off of its contact 7L Upon the return-of the dial? 12 however theroller 14 steps from one tooth to another on the star. wheel 16 and there 6 and 7 a number of times equal to the first figure in the deslred subscribers number.

The original actuation of relay'120, Flg.

. 2, completed the circuit from the battery wire 29 through the coil of slow-acting relay 126, conductor 181, contacts 130 and 128 of relay 120, conductor 148, and contacts 149.

and 150. of relay 104 to ground. The current in this path caused the actuation of the slow abnormal positions. 1 p

The interruption of V the current" through acting relay 126moving its contacts to their In the present system however the the coils of relay 120,- ca us'edby the rotation a' similar periodic deenergization of relay 120, butfthe relay126, being made slow actingyby means of a copper shell about its core, remainsinits actuated condition durof the dial at'the subscribers station, causes 9 ing the periodic interruption of'thecurrent I through its coil due to the release of the relay 120. Therefore at each release of the armature 128 of relay 120 a circuit is closed from the battery conductor 29 through eon;

. cluctor 163, the'coi-l ofthe vertica-l 'motormagnet 162, conductor 161, contacts 160 and 155 of relay 141,; conductor 154, the now closed contacts 158 and 152 of relay 126, contacts 129 and 128 of relay 1 20, conductor 148' and contacts 149 and'150 of relay 104 to earth. *The current in thispath actuates the vertical motor-magnet, stepping the shaft 225- up step by step-to a' position corresponding to the number of l impulses sent over theline bythe rotation of the dial atthe subscribers station. At the same time the'slow acting" relay 138 is actuated ifrom remain continuously actuated, the ground connection will still'bemaintained on the may be traced" from ground through the back contacts 123 and 127 of relay120, con tacts 182 and 180 of relay 126, contacts 185 and-147 ofrelay 133,contacts 146 and 125 1 otrelay 126 'to'conductor 96. At the terniination'of the first set of impulses sent from the-calling subscribers station the relay i188 falls'back to its normal'condition and thereupon completes-a; circuit from the battery conductor 29 through conductor 197,0011 of-relay 141, conductor 196, contactsj195 a-nd194', conductor 193, normally closed contacts .192 and'l91 of the rotary ofl' normal set offspringsj, condu ctor 190 and the now closed contacts 189 and'188 of the vertical oifnorm'al springs to'ground. The currentin this path actuates relay 141 changing'its contacts to their abnoramlposi tions. In the meantime the calling subscriber has moved his dial to a position-con.

private eonductor96-through a path which responding to the last figure in the desired number andnowreleases the dial, sending a corresponding number'o'f impulses over the I telephone l1ne.' Relay 120 IS again periodi- 'cally' released which now closes'a circuit duc tor 163, the eoil of therotary motor-magnet 166, contacts 164and 1'55 of the now actuatedrelay 141, conductor 154, contacts from the battery conductor29 through consince a new circuit is immediately estab lished from battery conductor 29 through conductor 197, coil of relay 141, conductor 196, contacts 195 and 201 of relay 138, conductor 200, the now closed contacts 199 and 191 of the rotary off-normal set ofsprings, conductor 190 and contacts 189 and 188 of the vertical oif-normal set of springs to ground. At the termination of this last set of impulses sent from the subscribers sta-' tion, relay 120 remains actuated and relay 138 therefore returns to its normal position. The severing of its contacts 195 and 201 now interrupts the circuit of relay 141 since con- 211 and 150 which complete the circuitof,

' ductor 193 is now open at the contacts of the rotary off-normal springs.

When the relay 141 returns to its normal position a ground connection is established through its contacts 145 and 142 and conductor 143 upon the private wiper 144 and private conductor 45 thence through contacts 46 and 53 of relay 24, contacts 54 and 55 of relay 28' and the coil 57 of cutoff relay 22 to the live pole of battery A. The current in this path actuatcs the cutoff relay 22 which frees the line from its normal connections with the line relay. The

ground "connection with private conductor 45 establishes the busy condition upon this conductor for purposes. hereinafter explained The release of relay-141 establishes a pathfor current from the battery conductor 29 through conductor 197, the coil 204 of relay 104, contacts 203 and 202 of relay 141, conductor 200, contacts 199 and 191 of the rotary ofi-normal set of springs, conductor190 and contacts 189 and 188 of the vertical off-normal set of springs to ground. The current in this path actuates relay 104, extending the talking circuit through contacts 102 and 103'and contacts 112 and 113 to the outside contacts 105 and 114 of ringing relay. 107 At the same time the actuation of relay 104 closes its contacts the ringing relay 107 from batteryconductor 29 through interrupter 173, brush 214, the coil of ringing relay 107, conductor 213, contacts 212 and 210 of relay 177 and con tacts211 and 150 of relay 104 to ground. The current in this path causes the periodic actuation and release of the ringing-relay 107. QlVhenever this relay is actuated its contacts 106. and 115 are connected with the inside contacts 225 and 226 whichextend to the brushes 227 and 228 of the alternating current ringing generator 229, thus periodically sending ringing current over conductors 108 and 116 and through the brushes 109 and 117 and contacts 71 and 72 over the desired telephone line to the substation. Before the ringing current is applied however the release of relay 141 has placed a ground connection through its contacts 145 and 142, conductor 143, brushes 144, private conductor 45, contacts 46 and 53 of relay 24, contacts54 and 55 of relay 28, conductor 56 and the coil 27 of cut-ofi relay 22 to the battery conductor 29. The current in this path has actuated the cut-0E relay 22 which extends the bank contacts 71 and 72 of t 1e connector switch directly through conductors 7 0 and 69, contacts 30 and 20 and 31 and 25 of cut-off relay 22 and line conductors 4 and 5-to the condenser 2 and annunciator 3 at the desired subscribers station.

When the desired subscriber answers his call by the removal of his receiver from the switch-hook a path for current is completed, during the interrupted period of the ringing relay 107, from battery conductor 29 through the coil 207 of relay 177, conductor 111, contacts 112 and 113 of relay 104, contacts 114 and 115 of relay 107, conductor 116, brush 117, contacts 72, conductor 69, conductor 32, contacts 30 and 20 of relay 22', conductor 4, switch-hook 11, receiver 10, transmitter 9, line conductor 5, contacts 25, and 31 of relay 22, conductors 33 and contact 71, brush 109, conductor 108, contacts 106 and 1050f relay 107, con tacts 103 and 102 or relay 104, conductor 101 and the coil 206 of relay 177 to ground. The current in this'path actuates relay 177. The actuation of this relay interrupts the circuit of the ringing relay 107 atcontacts 212 and 210 of'relay 177 and closes a circuit from battery conductor 29 through the coil 217 of relay 133, contacts 216 and 210 of relay 17 7 and contacts 211 and 150 of relay 104 to ground. The current in this latter path actuates relay 133. The actuation of relay 133 closes a locking circuit for that relay from battery conductor 29 through its coil 135, contacts 134 and 132 of relay 133, centacts 130 and 128 ofrelay 120, conductor 148 and the coil 151 of relay 104 to ground.

This locking circuit'also being a locking cirthe connecting circuit, which are now'maintained actuated, are relays 126, 104: and 135, the relays 14:1, 138 and107' being now in their normal conditions.

coils 206 and 207 of the bridged relay177. This relay therefore resumes its normal position and in so doing completes, a circuit from battery wire 29 through interrupter 173, brush 172, conductor 171', coil of release magnet 170, conductor 17 1, contacts 175 and 176 of relay 177 contact-s 18 1and 185 of the now actuatedrelay 133, conductor 186 and contacts 183 and 188 101' the'vertical off-- normal'set of springs to ground. Thecurrent in this path actuates'the release magnet 170 which,'through its action upon the dou ble release dog 240,,permits the shaft 235 to.

return to its normal position both as to -]rotary and vertical displacement. Upon the return of the shaft 235' to its normal position, the circuit through the release magnet is again interrupted at contacts 183 and 188.

of the vertical off-normal springs, these springs being now separated. When the calling subscriber replaces his telephone upon its hook the circuit through the coils 121 and 122 ofrelay 120 issevered.-*Re1ay-' 120 therefore returns toits normal condition and upon so doing interrupts the circuits through the coil of relay 126 at' contacts 130 and 128 and at the same time in-e terrupts the'locking circuits of relays 133 and 104. The release ofrelays 120'and 126 removes the ground connection from pri-: vate conductor 96 thus allowing the line circuit relays to resume their normal positions. Thus all ofthe relays associated with the line and. connecting circuits are returned to their normal conditions and the circuits may: be used again for completing another ing a new call by having his' receiveroflj.

the hook at thegtime the" calling subscriber disconnects, provision s made whereby the connecting switch will not be disconnected,

but only the apparatus carrying the connection from the calling subscriber to the con-,

nector switch will be released. Thus when the calling subscriber replaces his recelver before thecalled subscriber has replacedhis the relay 120 is released whereas the relay 177 remains in its actuated condition.

In this instance, in'order to 'ductor .96, through contacts 124 and 123 of I that relay, but upon the return of relay 126 to its normal condition the ground connection is reestablished upon private conduc- If now the called subscriber is thefirst to replace his receiver upon the switch-Z hook the circuit is interrupted through the V 1133, c0nductor'186and contacts 183'and 188 [of the vertical otf-nor nalsprings. In this tor 96 through contacts 125and 209 of relay 126, contacts 208 and 176 ofthe actuatedarela 17 7 contacts and 185 of rela manner, although the apparatus used in completing the. connection between the callmg subscribers line and the connector cir- I "the private'conductor 96 so thatthe connector circuit will not again be selected. When the called subscriber now replaces his receiver upon the hook thecircuit is interrupted through coils 206and 207 of relay 177, permitting that relay to return toits normal condition; Upon so .doing'a circuit is established as formerly described through the release magnet 17O "which actuates that normal condition. I It frequently occurs that a desired line is busy, and therefore means are provided to notify thecalling subscriber ofthe busy condition of the desired line. The various operations for completing a connection" will in this case be carriedout'the same as previously described until thelastimpulse has been sent "from y the calling subscribers station and the wipers of the connector switch arrive upon the contacts of' thedesired line. if this line is busy either as a calling or a called telephone'line, its private contact 15 is grounded and thereforewhen normal "condition," a circuit is established from the ground pole ofbattery a't-brushes ltthrou'ghconductor 143, contacts 142 and actuates relay 133. Thea'ctuation of this 'magnet to returnthe connector switch to its V the impulses from the subscribers dial have I ceased and the relay 138 has resumed its relay closes its contacts 184 and 18.5, thus completing a circuit from batteryconductor '29 through interrupter'17 3, brush 172, conductor 171, the coil ofthelrelease magg net 170, conductor 174, contacts 175 and 17 6 of relay 177, contacts 184 and'185 of relay133, conductor-186 and contacts 183 and switch to its'normal conditionwhich again interrupts the circuit of the release magnet. The actuation of relay 133 also closes its contacts 220 and. 219 completing a" circuit from the busy tone producer 222 through the coil 221, contacts ,220 and 219 of relay 133, conductor 218, contacts 217 and 1120f relay 104, conductor 111, condenser "11 0 and over the path previously described through the receiver at the calling subscribers station and back to earth through the coils 121 and 206 of relays 120 and 177. This notifies the calling subscriber that the desired line is busy and he therefor replaces his receiver upon the switch-hook and releases the apparatus in the manner previously described.

lVhen substation 1 desires a connection through the central oflice with either an automatic subscriber or another manual subscriber, the receiver 10 is removed from the switch-hook in the usual way, thus coinpleting a circuitfrom battery conductor 29 through the coil 27 of line relay 28, contacts 26 and 31 of relay 22, line conductor 5, transmitter 9, receiver 10, switchhook 11 line conductor l, contacts 20 and 21 of cut-off relay 22. and coil 23 of relay 24 to earth. The current in this path actuates-relays 28' and 24:. The actuation of relay 28 completes a circuit from the battery conductor 29 through interrupter 65, the coil of motor-magnet 64, contacts 63. and 62 of relay 28, contacts 61" and lS'of relay 22, contacts 46 and 49 of relay 23, conductor 50, segment 51 and the various busy or grounded contacts of the line switch to earth, thus moving the spider of the line switch step by step until the private wiper 83 is moved onto a nongrounded contact 93. When a nongrounded contact is reached, or if the private wiper normally stood upon a nongrounded contact there is no movement and current now flows from the battery conductor 29, through interrupter 65, coil of motor-magnetfi, contacts 63 and 62 of relay 28', contacts 61 and 48 of relay 22. conductor 4A, contacts l3 and 42 and coil 41 of relay 28, conductor Q0 and the coil 38 of relay 22 to ground.

, The current in this path actuates relay 22" closing a locking circuit forall three of the relays which may be traced from battery conductor 29 through the coil 57 of relay 22, the coil 58 of relay 24, conductor 59, contacts 60 and 48 of relay 22, contacts 443 and 42 and coil 4:1 of relay 28, conductor l0 and the winding 38 of relay 22' to ground.

The relays 22 and 24: now being actuated, line conductors land 5 are extender through conductors32 and 33 and the contacts 75 and 76 to the segments 77. and 78' of the line switch and thence through wipers 82 and 84 and contacts 91 and 92 to the talking conductors 94 and 95 which extend to the cord circuit shown upon Sheet 3' of the drawing. A circuit is therefore immediately completed from the live pole of battery A, Sheet 3, through the coil of relay 261, conductor 95, contact 92 of the lineswitch, Sheet 1,7brush 84, segment 7 8,

contacts 76' and 35 of relay 24-, conductor 33, contacts 31 and25 of relay 22, conductor 5, transmitter 9, receiver 10, switchhook 11 line conductor 4 contacts 20" 50, contacts l9 and l6 of relay 24, con- 7 tacts 48 and 60 of relay 22, conductor 59, coil 58 of relay 24: and coil 57 of relay 22 to the battery conductor 29. The current in this path maintainsthel actuation of relays 22 and 24', but the ground upon the private conductor places a shunt about the coil 41 of relay 28 thus allowing that relay to return to its normal condition.

. The actuation of relay 261 completes' the circuit of the call lamp 282 from the live pole of battery A through the lamp, con tacts 2S0 and281 of relay 261, and contacts 283 and 284 of relay 263 to ground- The operator, observing the display of the call lamp 2S2, actuates her listening key 249 and thus places her receiver 29% and the condenser 295 in a bridge between the talking conductors 246 and 255. The operator now obtains the number of the'desired subscribers telephoneandtests the sleeve or test contact of the multiple ack of said line by touching the tip 252 of her calling plug to the sleeve of the jack of the desired line. If the line is busy either as a callingor a called line the sleeve contacts of all of its inultlple jacks will be maintained at a .potential higher than that of ground and current will therefore flowjfrom the sleeve of the tested jack over the tip 252, contacts 251 and 250 ofthe operators ringing key, auxiliary contacts 299 and 300 and the tertiary winding of the operators induction coil to ground. The current in this path causes inductive disturbance in the secondary winding of the operators induction coil which is heard by the operator and thus indicates in the usual way that the line is busy.-

Assuming however that the line is found idle the operator inserts her calling plug completely into the jack of the desired line and causes the tip ring and sleeve contacts 252, 259 and 258 to electrically connect with the tip ring and sleeve contacts 73, 79 and 'Tl'of the desired line, for convenience assuming the desired line to'be that of substation l, though it may be another manual telephone line. 7

The operator now actuates her ringing key causing its contacts 251 and 257 to register with contacts 301 and 302. A circuit is thus established from battery conductor 29 through the non-inductive resistance 304, contacts 302 and 257 of the ringing key, sleeve contacts 258 and 74 of the plug and jack, conductor 70, contacts 35 and -36 of relay '24, conductor 40, and to coil 38 of cut oil relay 22 to ground. The current in this path actuates relay 22. A" circuit is noW completed from the ringing generator 305, Sheet 3, through contacts 301 and 251 of the ringing key, tip contacts 252 and 73 of the plug and jack, conductor 69, conductor 32, contacts 30 and 20 of the noW actuated relay 22, line conductor 4, annunciator 3, condenser 2, contacts 7 and 6 of the subscribers impulse mechanism, line conductor 5, contacts 25 and 31 of cut-off relay 22, conductors 33 and 70, sleeve contacts 74 and 258 of the jack and plug, contacts 257 and 302 of the operators ringing keyand the noninductive resistance 304 to the battery conductor 29. The current in this path being alternating in character sounds the annunciator 3 at the station of the desired subscriber. I p

The operator now releases her ringing key and thereby completes a circuit from the live pole of battery A through the coil of relay 263, conductor 255, contacts 256 and 257 of the operators ringing key, sleeve contacts 258 and 74 of the'plug and jack, conductor 70, contacts 35 and 36 of relay 24, conductor 37 and the coil 38 of cut-ofi relay to ground. The current in this path maintains the actuation ofcut-ofi' relay and actuates relay 263. The actuation of relay 263 interrupts the circuit of call lamp 282 at contacts 283 and-284 and completes the circuit of the calling lamp 289 at contacts 284 and 286. The actuation of relay 263 also disconnects the private conductor 96 from the common point 270 and connects it to ground'through contacts 268 and 290. It may here be'noted that the actuation of relay 260 not only grounded the private conductor 96, but also through conductor 267 and contacts 268 and 269 of relay grounded the common conductor 270. This common conductor-extends preferably to one half of the cord circuits appr zaring at a single operators position and therefore during the time that relay 260 is actuated and before relay 263 is actuated, all of the private Wires Which are normally connected to the conductor 270 aregrounded, which prevents other calls from being connested With the cord circuits of this particular group -Wl1ll6 the operator is'busy answering one call. The actuation of relay also closes contacts 291 and 292which complete a shunt about the contacts 247 and 248 of the operators listening key.

257 of the operators ringing key, sleeve con tacts 258 and 74 of the plug and jack, conductors 70 and 33, contacts/31 and 25 of cut-oh relay 22, line conductor 5, contacts 6 and 70f the subscribers interrupter, transmitter 9, receiver 10, switch-hook 11, line,

conductor 4, contacts 20 and 30 of relay 22, conductors 32 and 69,tip contacts 73 and 252 of the jack and plug, contacts251 and 250 of the operators ringing key, contacts 248 and 247 and contacts 292 and 291 in parallel, conductor 246 and the coil of re-'- lay 262 to the ground pole of battery A. The current in this path actuates relay 262 separating its contacts 287 and 288 and thus 'effacing the calling lamp 289. The calling and called subscribers are nowin conversation and all, signals are efi'aced' at the central ofiice. The current for the transmitterof the calling line is fed through the coils ofrelays 260 and 261 and the current for the transmitter of the called line is fed through the coils of relays 262 and 263.

lVhen both the calling and called subscribers replace their receivers upon their respective switch-hooks, the circuits are in terrupted through relays 260 and 261 and through relay 262. The release of relay 260 does not remove the ground connection from the' private conductor 96 for the reason that this conductor is grounded through conductor 267 and contacts 268 and 2900f relay 263. The release of relay 261 now completes the circuit of the call'lamp 282 from the live pole or battery A through the ground. Therelease ofrelay 262 completes the circuit of the calling lamp 289 from the live pole of'battery A through therlamp,

7 contacts 288 and 287 'ofrelay 262 and contacts 286 and 284 of relay 263 to ground. The display of signals 282 and 289 indicates to the operator that the subscribers have both replaced their, receivers upon their respective switch-hooks and she then removes her calling plug from the jack which severe the circuit of relay 263. The renection from the private conductor 96 allowing the relays 24 and 22 to return to lease of relay 263 removesthe ground conremoval of the calling plug'also interrupts the circuit through the coil38 of relay 22, thus allowing that relay-to return to normal. The apparatus hasnoW allreturned to normal and is in condition for another call.

, It-vvill be seen that theline circuit ofmy invention, here illustrated, may be operated either With a full automatic telephone systom or a calldistributing telephone system, and that I have provided a system in which subscribers may be provided with either call-distributing or full automatic service according to their desires.

The private contacts of the automatic connector switch multiple are carried to the ring contacts 79 of the multiple acks and the ring contacts 259 of all of the cord cir cuits are grounded so that the insertion of a plug into one of the multiple jacks places the busy condition upon the private contacts of this line throughout the automatic connector switch multiple. Likewise when a connection is established through the automatic connectorswitch with any line, the sleeve contacts of all of the multiple jacks are raised to a potential above ground through contacts 35 and 36 of relay 24. In this manner an automatic and a manual connection will not be established with a single line at the same time. \Vhile I have shown and described my invention with reference to a particular embodiment it is to be understood that alterations may be made therefrom without departing from the spirit or scope or my invention.

Vhat I claim is 1. In a telephone system, the combination with manual andautomatic telephone lines, of connecting means at the central or'lice for establishing either manual or automatic connections with either of said lines, the establishment of an automatic con -ection with either otsaid lines being adapted to place battery potential upon the test contacts oi the manual connecting means and ground potential upon the test contacts of the automatic connecting means to indicate that the line is busy both for automatic and manual connections, and the establishment of a manual connection with either of said lines being adapted to indicate that the line is busy both for manual and automatic connections.

2. In a telephone system, tie combination with a telephone line, of multiple aclis and 2 multiple automatic connector contacts for said line, a cut-off relay. for the line and .nieans to actuate said cut-oil" relay either by the establishment of a manual connection .with said multiple acks or by the establisln with a telephone line, of multiple jacks and multiple automatic conector contacts for said.

line, a cord circuit and a connector switch, a cut-off relay for theline, the establishment of a connection between either the cord circuit or the automatic connector switch and said line, being adapted to connect the grounded pole of battery with the private contacts of the connector switch multiple and the non-grounded pole of battery with the test contacts of the multiple jacks.

4. In a telephone system, the combination with a telephone line, of a cut-off relay for the line, a central source of current, contacts for establishing a connection with said line, a pair of conductors extending from said contacts to the line circuit, a cut-oil relay for the line having a coil normally connected between one of said conductors and the ground pole of the main battery, a third conductor, said cut-off relay having a coil connected between the live pole of the main battery and said third conductor.

5. In a telephone system, the combination with a telephone line, o-fmultiple jaclrs'having a pair of conductors for establishing a connection with said line, a cut-off relay for the line'having a coil connected to one'ot' said conductors, an automatic connector switch multiple having said pair of wire. and a third wire for establishing a connection with said line, said cut-oil relay having a coil connected with said third wire.

6. In a telephone system, the combination with a telephone line, of a cut-off relay for the line, a pair or" conductors over which a conversational circuit is adapted to be completed when said line is called, and a third conductor independent of the talking circuit, said cut-off relay being adapted to be actuated either over one of said talking conductors or over said third conductor.

7. In a telephone system, the combination with calling and called subscribers lines, of a selector switch and a connector' switch serially connected to establish a talking circuit between said subscribers lines, multiple test or guard contacts between said selector and connector switches, a release circuit including one of said contacts and means responsive to the interruption of current in the calling subscribers line for momentarily removing and replacingthe guard potential of said mul tiple test contacts, and release mechanism for said selector switch actuatedby the momentary removal of the guard or test potential. 8. In a telephone system, the combination with a telephone line, multiple aclrs and multiple automatic switch contacts for said line, a central battery, a cut-oil relay for the line adapted to be actuated under two conditions, first by, the connection of one pole of said battery to multiple jack contacts of said line and second by the connection of the other pole ofsaid battery to multiple automatic connector contacts-of said line.

9. In a telephone system, the combination with a connector switch, oi a callmg and a called subscribers line adapted to be connected through said switch, selecting apparatus for establishing the connection between a'calling line and an idle connector switch,

a private conductor extending between the selective apparatus and the connector switch,

a relay in said conductor energizedduring conversation, said conductor being charged.

from the connector switch with busy potential during conversation to prevent other selector switches from connecting with the busy connector switch, the deenerglzation of said relay serving to. release the selecting apparatus when the calling subscriber replaces his receiver uponits hook, and means ally connected to establish a talking circuit between said subscribers lines, multiple test or guard contacts between said selector and connector switches, a release circuit including one of said contacts and means responsive tothe interruption of current in the calling subscribers line for-momentarily removingand replacing the guard potential of said multiple test contacts, release mechanism for said selector switch actuated by the momentary removal of the guard or test potential, and means controlled by .the interruption of the called subscribers circuit for thereafter continuously removing the guard potential from said multiple contacts,

11. In a telephone system, thecombination with a callingand a called telephone line, of

selector and connector switches connected in tandem for establishing a talking circuit 1- between said telephone lines, a private conductor extending between said-switches and charged with busy potential to prevent interference withthe establishedfltalking circuit,

being again selected. w

system, the combina tion with a pair of telephone lines, of aplui an electro-magnet for the selector switch maintained in actuated condition over said private conductor, and means associated with the connector switch for interrupting the circuit of said electromagnet torelease said selector switch, and means to reestablish the busy potential upon the interrupted portion of the private conductor extending to the connector switch to prevent said switch from 12. In a telephone rality of automatic switches, connected in series between the calling and'the called telephone line, a private conductor'e'xtend ing from one switch to its adjacent switch in the series, test contacts for the latter switch in electrical connection with said private conductor, a release relay for the one of said switches nearest the calling-line continuously actuated during the use of said switches by current flowing over the private conductor extending from said switch to the switchnext in series toward the called subscribers line, and means for interrupting said private conductorto bring about the release of said first switch, and meansoperating immediately thereafter to restore busy potential on the multiple testc'ontacts of the J second switch.

13. Ina telephone system, the combination with. an establishedta-lking circuit, of a pair ofserially connected switches having contacts included in said talking circuit, of

' a test and release trunk extending between said switches and including multiple test contacts, means under the control of the calling subscriber to release one of said switches and prevent the selection of the other of said switches, and means under the control of thecalled subscriber for releasing the other. of said switches withoutfreeing either of said switches for use, and means thereafter for, releasing one. of said switches and free mg the other for use.

14. Ina telephone system, the combination therefor and means to move said wiper into engagement w th various stationary contacts', a pair of electromagnets controlling contacts serially included in circuit with said testwiper, a test relay adapted to be connectedwith said test wiper by the release of ;.'one.or' sald electromagnets and again disconnectedtherefromby the release of the- .second]electromagnet, and a source of busy tone current connected with the conductors of the connector swltch through the actuation of said test relay. V 15. ln'a telephone system, the combinationwith a connector switch, of a test wiper engagement with various stationary contacts, a pair of electromagnets controlling contacts serially included in circuit with said test wiper, a test relay adapted to be connected with said testwiper by the release under the control of the calling subscriber 'with 'a connector-switch, of a test :wiper therefor' and means to nove'said wiper into llO of one of said electromagnets and again dissecond electromagnet, and'mea-ns responsive toithe release of said second electromagnet' for, applying busy potential to the test w per.

connected therefromby the release of the 16. In a telephone system, the combination I with a calling subscribers line and a plurality of subscribers lines to be called, of

a;test contact for each subscribers line and means to apply busy potential thereto when the subscribers line is in conversatlon, a

" connector switch and a movable test wiper therefor adapted to engage the test contact of a line when a connection is desired withsaid line, a pair of electromagnets for the connector switch and contacts controlled thereby and a circuit for the first completed operated upon the energization of said re by the actuation of the second, means to interrupt the circuit of the second after the arrival of the movable test wiper upon the test contact of a desired line, a test relay and a circuit therefor extending through contacts closed by the release of the second electromagnet and contacts to be opened by the release of the first electromagnet to said test wiper, whereby, it the called subscribers line is busy and therefore has busy potential upon its test contact current will flow through the coil of the test relay during the interval after the release of the second electromagnet and before the release of the first electromagnet.

17. In a telephone system, a line, a nonnuinerical trunking switch individual thereto, trunk lines for talking purposes leading therefrom, said switch having line wipers always in electrical engagement with some one of said trunk lines, which connected trunk lineiis always the one last employed by said switch for extending a call, normally open connections between said line and line wipers, a relay, means for energizing said relay over the linecircuit, and means lay to close said normally open connections.

18. In a telephone system, a line, a nonnumerical trunking switch, trunk linestor talking purposes leading therefrom, said switch having line wipers always in electrical engagement with some one of said trunk lines, which connected trunk line is always the one'last employed by said switch for extending a call, said switch having a step-by-step actuated shaft that always rotates in the Same direction, normally open connections between said line and line wipers, a relay, means for energizing said relay over the line circuit, and means operated upon the energization of saidrelay to close said normally open connections.

19. In a telephone system, an automatic trunking switch, trunk-lines for talking purposes leading therefrom, terminals forsaid trunk lines, said switch having line wipers always in electrical engagement with theterminals of some one of said trunk lines, which connected trunk line is alwaysthe one last employed by said switch for extending a call, a telephone line to which said switch is individual, a normally deenergized relay controlling, on energization, the connection between the said telephone line and switch,

' and means whereby said trunking switch.

will extend a connection over said connected trunk if the same is idle.

20. In a telephonesystem, a'line, numerical trunking switch, trunk lines for talking purposes leading therefrom, said switch having line wipers always in electrical engagement with some oneof said trunk lines, which connected trunk line is always the one last employed by said switch for exa non:

tending a call, means for controlling said switch over the two sides of a metallic line circuit in series, normally open connections between said line and line wipers, a relay, means for energizing said relay over the line circuit, and means. operated upon the energization of said relay to close said normally open connections.

21. In a telephone systenna non-numerical trunking switch, trunk lines for talking purposes leading therefrom, said switch having line wipers always in electrical engagement with some one of said trunk lines, which connected trunk line is always the one last em ployed by said switch for extending call, an automatic selector switch at the other end of said trunk lines, and means for conemployed by said switch for extending a call,

an automatic selector switch at the other end of each of said trunk lines, and means for controlling said switches over two sides of a metallic line circuit in series.

23. In a telephone system, a non-numerical trunking switch, trunk lines for talkin purposes leading therefrom, said switch having line wipers always in electrical engagement with some one ofsaid trunk lines, which connected trunk is always theone last employed by said switch tor extending a call, other switches for using said trunk lines in extending calls, means allottedto each trunk line for causing said first-mentioned switch to antomatically select another trunk line it the one which it used last is busy whenit again responds to a call, normally open connections between said line and line wipers, a relay, means for energizing said relay over the line circuit, and means operated upon the energization of said relay to close said normally;

open connections. V

Qt. In a telephone system, an automatic trunking switch, trunk lines for talking purposes leading therefrom, terminals forsaid trunk lines, said switch vhaving line wipers always in electrical engagement with the terminals of some one of said trunk lines, which connected trunk line is always the one last employed by said switch for extending a call,

other switches for using saidtrunk lines in extending'calls, means allotted to each trunk line for causing said first-ment1oned switch to automaticallyselect another trunk line if the one which it used last is busy whenit again'responds to a call, normally open con nections between sa d line and line wipers, a

relay, means forenergizing said relay over the line circuit, and means operated upon the energization of said relay to close said norwhich connected trunk line is always the last one employed by said switch for extending a call, normally open connections between said line and line wipers, and a double-wound relay for controlling, upon energization, said normally open connections.

26. In a telephone system, a line, a non numerical trunking switch, trunk lines for talking purposes leading therefrom, said switch having line wipers always in electrical connection with one of said trunk lines, I

which connected trunk line is always the last one employed by said switch for extending a call, normally open connections between said line and line wipers, a double-wound relay .for controlling said normally open connections, means for energizing said relay to close said connections when connection is made with an idle trunk, and means for preventing said relay from energizing when said wi ers contact with a busy trunk.

signed by me at Rochester, county of Monroe, and State of New York, in the presence of two witnesses. I

CLIFFORD C. BRADBURY. lVitnesses FRANZ J. DoMMnR UE, CHARLES E. I'IAGUE. 

